Why is the Ocean Salty?
Rain water, or precipitation, is slightly acidic due to dissolved compounds. When this acidic water beats down on the land and rocks, they end up dissolving the minerals in the rocks and return them to the water. The minerals are salt compounds-- not just sodium chloride. A salt is any ionic compound (metal and a nonmetal), such as calcium chloride or magnesium chloride. The salt(s) then flow down rivers and streams to their final destination in the oceans, where they remain. Over the course of millions of years, this salt has accumulated to be a substantial component of the oceans.
All types of water, even water from rain that contains dissolved chemicals. scientists call these "salts." But not all water tastes salty. Water is fresh or salty according to individual judgment, and in making this decision man is most convinced by his sense of taste than by a laboratory test. It is one's taste buds that accept one water and reject another.
One simple experiment illustrates this. Fill three glasses with water from the kitchen faucet. Drink from one and it tastes fresh even though some dissolved salts are naturally present.
Obviously, the ocean, in contrast to the water we use daily, contains unacceptable amounts of dissolved chemicals; it is too salty for human consumption.
HOW SALTY IS THE OCEAN?...
How salty the ocean is, however, defies ordinary comprehension. Some scientists estimate that the oceans contain as much as 50 quadrillion tons of dissolved solids.
If the salt in the sea could be removed and spread evenly over the Earth's land surface it would form a layer more than 500 feet thick, about the height of a 40-story office building. The saltiness of the ocean is more understandable when compared with the salt content of a fresh-water lake. For example, when 1 cubic foot of sea water evaporates it yields about 2.2 pounds of salt, but 1 cubic foot of fresh water from Lake Michigan contains only one one-hundredth (0.01) of a pound of salt, or about one sixth of an ounce. Thus, sea water is 220 times saltier than the fresh lake water. What arouses the scientist's curiosity is not so much why the ocean is salty, but why it isn't fresh like the rivers and streams that empty into it. Further, what is the origin of the sea and of its "salts"? And how does one explain ocean water's remarkably uniform chemical composition? To these and related questions, scientists seek answers with full awareness that little about the oceans is understood.
THE ORIGIN OF THE SEA...
In popular language, "ocean" and "sea" are used interchangeably. Today's seas are the North and South Pacific, North and South Atlantic, Indian and Arctic Oceans and the Antarctic waters or seas.
Scientists believe that the seas are as much as 500 million years old because animals that lived then occur as fossils in rocks which once were under ancient seas. There are several theories about the origin of the seas, but no single theory explains all aspects of this puzzle. Many earth scientists agree with the hypothesis that both the atmosphere and the oceans have accumulated gradually through geologic time from some process of "degassing" of the Earth's interior. According to this theory, the ocean had its origin from the prolonged escape of water vapor and other gases from the molten igneous rocks of the Earth to the clouds surrounding the cooling Earth. After the Earth's surface had cooled to a temperature below the boiling point of water, rain began to fall and continued to fall for centuries. As the water drained into the great hollows in the Earth's surface, the primeval ocean came into existence. The forces of gravity prevented the water from leaving the planet.
SOURCES OF THE SALTS...
Sea water has been defined as a weak solution of almost everything. Ocean water is indeed a complex solution of mineral salts and of decayed biologic matter that results from the teeming life in the seas. Most of the ocean's salts were derived from gradual processes such the breaking up of the cooled igneous rocks of the Earth's crust by weathering and erosion, the wearing down of mountains, and the dissolving action of rains and streams which transported their mineral washings to the sea. Some of the ocean's salts have been dissolved from rocks and sediments below its floor. Other sources of salts include the solid and gaseous materials that escaped from the Earth's crust through volcanic vents or that originated in the atmosphere.
The ocean is salty because the salt in the ocean comes from rocks on land. In fact, if the ocean’s salt was spread over land, then it would form a layer that is nearly 500 feet deep. That’s a little scary, but not as scary as whale sperm.
Another inportant thing that makes the ocean salty is the water runoff which pours into the ocean. This might seem counterintuitive to you, as rivers, streams, and lakes probably taste fresh to you. However, this water also contains dissolved salts, although the concentration is lower than that in the ocean. These salts make their way to the ocean with the river water, which eventually evaporates from the ocean to fall back to Earth again as rain, repeating the process.
SEA WATER IS NOT SIMPLE...
Scientists have studied the ocean's water for more than a century, but they still do not have a complete understanding of its chemical composition. This is partly due to the lack of precise methods and procedures for measuring the constituents in sea water. Some of the problems confronting scientists stem from the enormous size of the oceans, which cover about 70 percent of the Earth's surface, and the complex chemical system inherent in a marine environment in which constituents of sea water have intermingled over vast periods of time. At least 72 chemical elements have been identified in sea water, most in extremely small amounts. Probably all the Earth's naturally occurring elements exist in the sea. Elements may combine in various ways and form insoluble products (or precipitates) that sink to the ocean floor. But even these precipitates are subject to chemical alteration because of the overlying sea water which continues to exert its environmental influence.
HOW SEA LIFE AFFECTS SEA WATER'S COMPOSITION...
Inasmuch as the oceans receive most of their water from the rivers, the ratios (as distinguished from the total amounts) of different chemical constituents should be about the same in both regardless of total salt content. But this is not so. Comparisons of Dittmar's data on ocean water with the average salt concentrations in river waters of the world is as shown on the preceding table .
SUMMARY...
The ocean is salty because of the gradual concentration of dissolved chemicals eroded from the Earth's crust and washed into the sea. Solid and gaseous ejections from volcanoes, suspended particles swept to the ocean from the land by onshore winds, and materials dissolved from sediments deposited on the ocean floor have also contributed. Salinity is increased by evaporation or by freezing of sea ice and it is decreased as a result of rainfall, runoff, or the melting of ice. The average salinity of sea water is 35 o/oo, but concentrations as high as 40 o/oo are observed in the Red Sea and the Persian Gulf. Salinities are much less than average in coastal waters, in the polar seas, and near the mouths of large rivers.The concentration of salt in seawater (salinity) is about 35 parts per thousand. Stated in another way, about 3.5 percent of the weight of seawater comes from the dissolved salts; in a cubic mile of seawater, the weight of the salt (in the form of sodium chloride) would be about 120 million tons.
By some estimates, if the salt in the ocean could be removed and spread evenly over the Earth’s land surface it would form a layer more than 166 meters (500 feet) thick, about the height of a 40-story office building.
Ocean salts, however, have no place to go. “The ions that were put there long ago have managed to stick around,” McKinley says. “There is geologic evidence that the saltiness of the water has been the way that it is for at least a billion years.”
Rain water, or precipitation, is slightly acidic due to dissolved compounds. When this acidic water beats down on the land and rocks, they end up dissolving the minerals in the rocks and return them to the water. The minerals are salt compounds-- not just sodium chloride. A salt is any ionic compound (metal and a nonmetal), such as calcium chloride or magnesium chloride. The salt(s) then flow down rivers and streams to their final destination in the oceans, where they remain. Over the course of millions of years, this salt has accumulated to be a substantial component of the oceans.
All types of water, even water from rain that contains dissolved chemicals. scientists call these "salts." But not all water tastes salty. Water is fresh or salty according to individual judgment, and in making this decision man is most convinced by his sense of taste than by a laboratory test. It is one's taste buds that accept one water and reject another.
One simple experiment illustrates this. Fill three glasses with water from the kitchen faucet. Drink from one and it tastes fresh even though some dissolved salts are naturally present.
Obviously, the ocean, in contrast to the water we use daily, contains unacceptable amounts of dissolved chemicals; it is too salty for human consumption.
HOW SALTY IS THE OCEAN?...
How salty the ocean is, however, defies ordinary comprehension. Some scientists estimate that the oceans contain as much as 50 quadrillion tons of dissolved solids.
If the salt in the sea could be removed and spread evenly over the Earth's land surface it would form a layer more than 500 feet thick, about the height of a 40-story office building. The saltiness of the ocean is more understandable when compared with the salt content of a fresh-water lake. For example, when 1 cubic foot of sea water evaporates it yields about 2.2 pounds of salt, but 1 cubic foot of fresh water from Lake Michigan contains only one one-hundredth (0.01) of a pound of salt, or about one sixth of an ounce. Thus, sea water is 220 times saltier than the fresh lake water. What arouses the scientist's curiosity is not so much why the ocean is salty, but why it isn't fresh like the rivers and streams that empty into it. Further, what is the origin of the sea and of its "salts"? And how does one explain ocean water's remarkably uniform chemical composition? To these and related questions, scientists seek answers with full awareness that little about the oceans is understood.
THE ORIGIN OF THE SEA...
In popular language, "ocean" and "sea" are used interchangeably. Today's seas are the North and South Pacific, North and South Atlantic, Indian and Arctic Oceans and the Antarctic waters or seas.
Scientists believe that the seas are as much as 500 million years old because animals that lived then occur as fossils in rocks which once were under ancient seas. There are several theories about the origin of the seas, but no single theory explains all aspects of this puzzle. Many earth scientists agree with the hypothesis that both the atmosphere and the oceans have accumulated gradually through geologic time from some process of "degassing" of the Earth's interior. According to this theory, the ocean had its origin from the prolonged escape of water vapor and other gases from the molten igneous rocks of the Earth to the clouds surrounding the cooling Earth. After the Earth's surface had cooled to a temperature below the boiling point of water, rain began to fall and continued to fall for centuries. As the water drained into the great hollows in the Earth's surface, the primeval ocean came into existence. The forces of gravity prevented the water from leaving the planet.
SOURCES OF THE SALTS...
Sea water has been defined as a weak solution of almost everything. Ocean water is indeed a complex solution of mineral salts and of decayed biologic matter that results from the teeming life in the seas. Most of the ocean's salts were derived from gradual processes such the breaking up of the cooled igneous rocks of the Earth's crust by weathering and erosion, the wearing down of mountains, and the dissolving action of rains and streams which transported their mineral washings to the sea. Some of the ocean's salts have been dissolved from rocks and sediments below its floor. Other sources of salts include the solid and gaseous materials that escaped from the Earth's crust through volcanic vents or that originated in the atmosphere.
The ocean is salty because the salt in the ocean comes from rocks on land. In fact, if the ocean’s salt was spread over land, then it would form a layer that is nearly 500 feet deep. That’s a little scary, but not as scary as whale sperm.
Another inportant thing that makes the ocean salty is the water runoff which pours into the ocean. This might seem counterintuitive to you, as rivers, streams, and lakes probably taste fresh to you. However, this water also contains dissolved salts, although the concentration is lower than that in the ocean. These salts make their way to the ocean with the river water, which eventually evaporates from the ocean to fall back to Earth again as rain, repeating the process.
SEA WATER IS NOT SIMPLE...
Scientists have studied the ocean's water for more than a century, but they still do not have a complete understanding of its chemical composition. This is partly due to the lack of precise methods and procedures for measuring the constituents in sea water. Some of the problems confronting scientists stem from the enormous size of the oceans, which cover about 70 percent of the Earth's surface, and the complex chemical system inherent in a marine environment in which constituents of sea water have intermingled over vast periods of time. At least 72 chemical elements have been identified in sea water, most in extremely small amounts. Probably all the Earth's naturally occurring elements exist in the sea. Elements may combine in various ways and form insoluble products (or precipitates) that sink to the ocean floor. But even these precipitates are subject to chemical alteration because of the overlying sea water which continues to exert its environmental influence.
HOW SEA LIFE AFFECTS SEA WATER'S COMPOSITION...
Inasmuch as the oceans receive most of their water from the rivers, the ratios (as distinguished from the total amounts) of different chemical constituents should be about the same in both regardless of total salt content. But this is not so. Comparisons of Dittmar's data on ocean water with the average salt concentrations in river waters of the world is as shown on the preceding table .
SUMMARY...
The ocean is salty because of the gradual concentration of dissolved chemicals eroded from the Earth's crust and washed into the sea. Solid and gaseous ejections from volcanoes, suspended particles swept to the ocean from the land by onshore winds, and materials dissolved from sediments deposited on the ocean floor have also contributed. Salinity is increased by evaporation or by freezing of sea ice and it is decreased as a result of rainfall, runoff, or the melting of ice. The average salinity of sea water is 35 o/oo, but concentrations as high as 40 o/oo are observed in the Red Sea and the Persian Gulf. Salinities are much less than average in coastal waters, in the polar seas, and near the mouths of large rivers.The concentration of salt in seawater (salinity) is about 35 parts per thousand. Stated in another way, about 3.5 percent of the weight of seawater comes from the dissolved salts; in a cubic mile of seawater, the weight of the salt (in the form of sodium chloride) would be about 120 million tons.
By some estimates, if the salt in the ocean could be removed and spread evenly over the Earth’s land surface it would form a layer more than 166 meters (500 feet) thick, about the height of a 40-story office building.
Ocean salts, however, have no place to go. “The ions that were put there long ago have managed to stick around,” McKinley says. “There is geologic evidence that the saltiness of the water has been the way that it is for at least a billion years.”
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